The present invention relates to a digital signal processing method for transmitting digital encoded video data and digital audio data.
In video data processors, recently, there is a rapid progress from analog to digital data, and further from non-encoded to encoded data reduced in bit rate. The professional video tape recorder (hereinafter called VTR), for example, has been evolved from analog recording system to such a digital VTR as D1, D2, D3 or D5 recording standard. Recording system of digital video signal has been further evolved from that of recording non bit rate reduced digital video signal to that of bit rate reduced one using high efficiency encoding technologies. Even in the consumer-use VTR, the analog system such as VHS has been evolved to such a recording system of high efficiency coding by Huffman code using discrete cosine transform (hereinafter called DCT) as DV-VTR system or D-VHS.
The conventional system has used the analog interface or serial digital interface (hereinafter called SDI) of non-encoded video data specified as SMPTE (Society of Motion Picture and Television Engineers) standard 259 M for video data transmission between studios for editing and/or broadcasting, between video systems.
However, in accordance with progress in digital apparatus as well as in high efficiency coding technology, it has been now the mainstream to transmit and receive encoded and bit rate reduced video data. In the consumer-use DV-VTRs, signals are exchanged by the interface of IEEE1394 standard among them. On the other hand, the professional VTR has used the serial digital transform interface (hereinafter called SDTI) standard for multiplexing plural channels of digital data encoded by bit rate reducing technology on the conventional SDI standard.
The SDTI standard is a system of multiplexing bit rate reduced data on the existing interface, and by increasing the bit rate to multiplex, it is easy to realize higher picture quality and faster transfer rate.
FIG. 7 is a schematic diagram of SDTI standard, showing the interface of SDTI standard of one video frame. FIG. 7a, FIG. 7b, and FIG. 7c correspond to images of 25, 50, and 100 mega bit per second (hereinafter called Mbps) modes, respectively, and bit rate reduced data of 25 Mbps, 50 Mbps, and 100 Mbps are transmitted on the interface of the SDTI standard.
In this case, each of the basic encoded and bit rate reduced digital data (hereinafter called basic data) of the professional VTR has the 25 Mbps bit reduced digital video data and 2-channel 16-bit digital audio data multiplexed thereon, for explanation.
Hereinafter, the data rate of video image are 25 Mbps, 50 Mbps, and 100 Mbps are called 25 Mbps mode, 50 Mbps mode and 100 Mbps mode, respectively.
The 25 Mbps mode of FIG. 7a, the 50 Mbps mode of FIG. 7b, and the 100 Mbps mode of FIG. 7c carry one basic data 1 in one video frame, two basic data 1 and 2 in one frame, and four basic data 1, 2, 3 and 4 in one frame respectively.
Thus, in order to improve the picture quality, the bit rate of basic data is to be increased on the interface of the SDTI standard, and bit rate of 100 Mbps is able to transmit and receive three types of encoded bit rate reduced digital data having 25 Mbps, 50 Mbps, and 100 Mbps.
Similarly, the 25 Mbps mode can transmit one set of 25 Mbps bit reduced data, and also the 50 Mbps mode can transmit, for example, two separate video data having bit rate of 25 Mbps.
Additionally, in the audio data processing, the digital audio data will be sophisticatedly multiplexed and then transmitted on the bit rate reduced video data in such multiple channel modes as 2 channels, 4 channels and 8 channels, and/or in such hierarchical sound qualities as 16 bits, 24 bits and 32 bits.
As one basic data has conventionally 2 channels audio data of 16 bits, the interface of the SDTI standard can transmit such multiple channel audio data as 2 channels digital audio data of 16 bits in the 25 Mbps mode of FIG. 7a, 4 channels audio data of 16 bits in the 50 Mbps mode of FIG. 7b, and 8 channels audio data of 16 bits in the 50 Mbps mode of FIG. 7c. 
The conventional SDTI standard can transmit the increased number of digital audio channels by the enhancement of transmission bit rate, but any technique has not yet been developed for improving the sound quality by using the audio data having more than 16 bits in transmission.
It is hence an object of the invention to present a processing method of digital signal for multiplexing audio data together with encoded and bit rate reduced video data in a specific fixed bit rate of one basic data, and transmitting and receiving it through a data bus, while keeping compatibility with the conventional data, and in a state applicable not only to multiple channels audio data but also to high quality audio data. It is another object of the invention to present a processing method of digital signal capable of transmitting and receiving audio data and video data hierarchically while keeping compatibility with the conventional data.
To achieve these objects, the digital signal processing method of the invention comprises the following steps.
(a) From digital video data, a plurality of first encoded video data and a plurality of second encoded video data, wherein a number of the first encoded video data is xe2x80x9cNxe2x80x9d (xe2x80x9cNxe2x80x9d being a natural number), and the second encoded video data is xe2x80x9cNxe2x80x9d;
(b) In audio data, each of Nxc3x97K channels (xe2x80x9cKxe2x80x9d being a natural number) of high quality quantized by M bits (xe2x80x9cMxe2x80x9d being a natural number) into audio data of upper L (xe2x80x9cLxe2x80x9d being a natural number) bits from most significant bit and audio data of lower M-L bits from least significant bit, wherein xe2x80x9cLxe2x80x9d is a quantized bits of standard audio data, and xe2x80x9cMxe2x80x9d is larger than xe2x80x9cLxe2x80x9d and no larger than twice of xe2x80x9cLxe2x80x9d (that is, L less than Mxe2x89xa62xc3x97L).
(c) A plurality of first basic data and a plurality of second basic data are composed,,
wherein number of the first basic data is xe2x80x9cNxe2x80x9d, and the first basic data have respective K channels audio data of upper L bits multiplexed together with each of the first encoded video data, and
wherein number of the second basic data is xe2x80x9cNxe2x80x9d, and the second basic data have respective xe2x80x9cKxe2x80x9d channels audio data of audio data of lower M-L bits multiplexed together with each of the second encoded video data.
(d) The first basic data are transmitted in a first data bus.
(e) The second basic data are transmitted-in a second data bus.